A highly representative cosmid library of Mbol partially digested human lung carcinoma DNA has been constructed. Important features of this library include the size of the cellular inserts (30-40 kb) and the presence of thymidine kinase and SV40 promoter sequences in the vector arms. A series of clones containing the complete c-fes and c-abl genes have been isolated, subcloned and subjected to detailed restriction endonuclease mapping.